Stop Hand Jitter

Import Talk animation you want to change and extend clip to avoid T-pose.

Bake Talk animation to CTRL Rig.
Delete Global CTRL and turn off leg IK.
Turn on Hand IK before frame 0 on Global CTRL.
Delete frames on HandFK, HandIK. Keep global frame.
Set scrubber to frame 0. Select Hand FK CTRL and parent constraint to Calf CTRL and bake. (Maintain and Dynamic Offset ON)
Set scrubber to frame 0. Select Hand IK CTRL and parent constraint to Calf CTRL and bake. (Maintain and Dynamic Offset ON)
Export new clip.

Rebuild Leg IK

Go to different sequence, import new clip with fixed hands and extend clip to avoid T-pose.
Bake to FK Rig.
Delete frames on FootIK l and r (Not Root).
Create new Override Layer with FootIK l and r.
Go to Override Layer, scrub to frame 0.
Import original Talk animation clip to unsure FootIK remains correct.

Rebuild Arm IK

Delete frames Hand IK l and r and Gun.
Create new Override Layer with Hand IK l and r and Gun.
Go to Override Layer, scrub to frame 0.
FIRST, select Gun IK and parent constraint to Hand R.
Select Right Hand IK and parent constraint to Hand R.
Select Left Hand IK and parent constraint to Hand L.
Turn off Maintain Offset and Bake from the drop down and NOT the button (doesn't generate all frames?)

If frames are glitchy, copy glitched frame to –1, then copy frame 1 to frame 0. If you have an animation you want to keep copy keyframes, bake constraints then paste keyframes so IK doesnt flip